How do we create `rtnl::routes::nla::NextHop` when we use in our codes?

[terassyi]

When we want to add a route that has multiple paths, we have to use rtnl::route::nlas::NextHop struct from our codes.
However, we cannot directly initialize this struct, because this struct has #[non_exhaustive] attribute.

Is there any way to create rtnl::route::nlas::NextHop?

netlink-packet-route/src/rtnl/route/nlas/next_hops.rs

Line 77 in 75ce74c

pub struct NextHop {

[jeff-hiner]

I just hit something similar when trying to update from 0.13 to 0.15. A lot of structs are now marked #[non_exhaustive] but don't provide fn new or similar to create them. This makes it impossible to create RuleHeader, RuleMessage, and other structs necessary for changing routes. It also makes creating a NetlinkMessage unnecessarily more awkward.

Why was this marker added to these structs in the first place? Core parts like fib_rule_hdr don't have a paired size_t in the C ABI calls, and therefore aren't going to have fields added because it'd be a breaking ABI change.

[jeff-hiner]

Caused by #11